Enfield and Whitehouse return with another loose collection of sketches, although be thankful that it's not as loose as their profoundly dodgy last series.

All their familiar obsessions are present: football managers (there's a very funny opening skit where an irate boss gives a half-time team talk in several different languages), class divides, stiff black-and-white films, and middle-aged men trying to have sex with gullible young women.

It has the age-old problem of sketches that don't build on their initial premise - see the 1940s Bourne Identity (Oh hell's bells, who the devil am I?), a funny idea that drifts on for about a week - and lot of the material is, in truth, a bit too familiar. But if, for instance, the elderly DJs who play nothing but hip-hop are one variation too many on an old gag, it doesn't matter when it's as well performed as this is.

The gabbling, Plasticine-faced surgeons, and the rabid northern man who lets out a pained squeak when told by his southern owner that he must be neutered, are rewind-and-play-it-again fantastic.

Dispensing with character and plot must be tempting for writers trying to create a zany sitcom. Anything can happen when you're not tied to a story, and if your protagonists aren't believable people, you can make them say anything that comes to mind.

Lab Rats hops gaily from one idea to the next and a lot of the broad visual jokes are funny. Co-writer Chris Addison does well in the Father Ted role of the only person who isn't eccentric to the point of mental illness (It's like being in a room full of my Gran!)

But the free-form silliness stops comic momentum building. If a gag fails, the audience have nothing else to hang onto - the loosely defined supporting characters can't even be relied on to do their funny thing, because you're not sure what that thing is.

Comedy like this is almost impossible to get right. Lab Rats valiantly fails.

The inessential comedy panel show returns for an astonishing sixth series, with Jimmy Carr again marshalling six comedians as they recite jokes based on surveys and statistics. Returning as team captains are Sean Lock, generally the best spontaneous contributor by far, and Peter Kay-ish Manchester comic Jason Manford.

It's all a bit stilted and choppily edited, but it can attract decent guests (Vic Reeves and Griff Rhys Jones were on last year - David Walliams appears tonight) and will do well in the ratings.